When it comes to tough tests, the notoriously punishing selection process for the SAS is among the longest and most punishing.

It lasts for five months and has a 90% fail rate – and this year, in a landmark and controversial moment for the British Special Forces, it will be open to women too.

Female candidates will face excruciating physical tests such as the infamous 24km "Fan Dance" across the highest mountain in the Brecon Beacons, and the top-secret mental assessment carried out as part of a 36-hour interrogation process.

And in the new season of hit TV show SAS: Who Dares Wins – which starts on Sunday – women will also compete on the show with men for the first time.

A man punches a female recruit in the face for the first time on the show (Image: Channel 4)

Laura reacts to white noise being played to her through headphones (Image: Adam Gerrard/Daily Mirror)

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It provides the first snapshot of what they might face if they want to succeed in joining the elite unit - and it includes humiliation, mental abuse and gruelling physical challenges.

For the first time in TV history in a non-dramatised programme, a man is also seen punching a woman in the face during the fighting challenge.

One of the show’s stars, Royal Marine Commando and Special Forces Sergeant Jason Fox, known as “Foxy”, says: “Everyone was individual, there were some weak women, there were some strong women, there were some weak men, there was some strong men. In the end it wasn’t really about gender.”

Laura found out what it was like to be taken hostage (Image: Adam Gerrard / Daily Mirror)

He thinks for a moment.

“Well, it was, but it wasn’t. We didn’t want it to be about gender – we wanted it to be about whether you could get to the end of the course. We knew there would be women who couldn’t do it, but we also suspected that there would be women who could do.”

And if anyone thinks women would be treated differently, think again. It seems the opposite is true.

In the first episode alone, the entire team is punished because some of the women keep their wet underwear on rather than going braless after diving into a freezing river in the Andes.

Chief Instructor Ant Middleton is seen telling the female recruits: “I thought you f*****g women would be a bit more switched on, a bit more f*****g smart, obviously not.

“I didn’t want to do this, have this men and women thing, but you f*****s are doing it.”

The show's men vs women fighting challenge

Laura found the training and tests brutal in the extreme (Image: Adam Gerrard / Daily Mirror)

During a brutal 3km mountain trek pulling a 120kg sledge, Middleton screams at the last four recruits: “Lo and behold the last four are f*****g chicks. Surprise f*****g surprise.”

As I join some of the first-ever female recruits on a training day in a military base in West Sussex, one says that throughout the controversial interrogation scenes, during which she was forced to strip naked, she wasn’t given any allowances for being on her period.

And as much as Foxy and his fellow comrades Matthew “Ollie” Ollerton and Mark “Billy” Billingham insist gender isn’t important, there are many aspects of the new selection process which clearly make them feel uneasy.

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While Ollie agrees that there are “some advantages” to women joining the special forces, he argues that they could change the “emotional dynamic of male and female interaction”.

Foxy says: “I would say emotional relationships are not a good thing when you’re getting shot at.”

Billy says: “The other issue we’ve got is that 90% of our work is beyond the enemy lines. There’s a 50% chance every time we go there of getting captured. Imagine a woman getting captured as part of our patrol? How we would feel? How the world media would feel?”

This year’s show follows a group of 25 men and women into the punishing Andes Mountains in Chile – the longest and toughest course ever designed.

Over 11 days winter warfare environment, with high altitude and snow storms, the recruits are tested to the extremes of their physical and mental capabilities.

As part of a special training day, I got just a tiny glimpse of the conditions the recruits faced.

Some of this year's recruits

Laura in her fatigues

Dressed in my army fatigues and weighed down by a big Bergen pack, Foxy, Ollie and Billy put me through my paces as I jogged, lunged, squatted and burpeed up acres of hilly forest. I have run marathons and consider myself to be fairly fit, but I felt far from it as I was ordered to haul a huge log up uneven terrain and thick mud.

And this was nothing compared to the real SAS selection candidates have to endure – I wasn’t even carrying the full 27kg (60lb) load on my back throughout the ordeal.

But no amount of running can prepare you for a breathtaking dive in deep, freezing waters in late December.

And then came the interrogation after we were captured by the “enemy”.

We were bundled into the back of a van as gunfire and explosions rang out, with bags put over our head and headphones blaring white noise put over our ears to rob us of our senses.